Add checkpoint metadata

models/grpo_mustard_dexpolicy_seed0.json

@@ -0,0 +1,12 @@
+{
+  "method": "GRPO + DexPolicy",
+  "object": "ycb-006_mustard_bottle",
+  "seed": 0,
+  "source_steps": 507904,
+  "additional_steps": 250000,
+  "learning_rate": 0.00005,
+  "exploration_std_start": 0.10,
+  "exploration_std_end": 0.03,
+  "credit_module": "grpo_rtg",
+  "curriculum_stage": 2
+}